Heatwave a precursor to long, hot summer ahead

That's the message from the Bureau of Meteorology, which is predicting that this week's heatwave will be just a taste of an extended hot and dry summer to come.

"Odds are in favour of hotter and drier conditions to the end of March," Karl Braganza, manager of climate monitoring at the Bureau of Meteorology, said

The current heatwave - possibly the largest in territorial extent since 1972 - is set to deliver maximum temperatures of 45 degrees or higher for as long as a week in desert regions. Large areas of New South Wales, Victoria and South Australia are likely to see the mercury reach 40 degrees or more each day for the period.

BoM records released today show Australia ended 2012 with record average maximum temperatures for the final four months of the year, setting up much of south-eastern Australia for high fire risks.

Average maximum temperatures for the past four months were 1.61 degrees above the 1961-90 average, at 32.47 degrees, narrowly exceeding the previous record for the period set in 2002.

The heat will be focused on internal regions.

The extreme heat comes after a year in which much of Australia went from wetter and cooler conditions than normal for the first three months of the year to hotter and drier ones by the end of December.

The overall figures for 2012 show the average temperature for the year was 0.11 degrees above the 1961-90 average of 21.81 degrees. Rainfall averaged 476 millimetres, compared with a 465-millimetre average over the 1961-1990 period - well down from the 699 millimetres recorded for the 2011.

The bureau noted in its report how much southern Australia in particular had dried out during the course of the year.

“The year also saw unusually persistent high atmospheric pressure near southern Australia,” the report said.

“This was associated with greatly suppressed westerly frontal and storm activity in south-west Australia, and indeed southern Australia as a whole, and was reflected in very poor winter–spring rainfall in many southern areas.”

Australia may be heading back towards the drier conditions seen before the two recent years of relatively wet conditions.

“That April-to-November period has been dry pretty much since the 1990s, and even in the last few years it has been reasonably dry in between the two really wet summer season,” Dr Braganza said.

“The fronts and changes that are coming through just don't have as much rain in them.”